I've stopped in a handful of times. Seems like they're selling the new stuff at the going rate in San Francisco (cf. American Cyclery, Freewheel, etc...). It's a very small shop, but they've always seemed to have more people working there than customers (being a co-op could explain that). I'm also, hands down an immediate fan of any shop that has a tool rental program (though the setup at The Freewheel Hayes is much better, Box Dog seems to have more floor space dedicated to tires than to tools).

Hard to say for the used stuff; this where they specialize. It's been hit or miss from what I've seen. The first time I went it nothing caught my eye, next time I had to keep myself from picking up a cross frame for $100. Used parts bins are also an excellent idea but I never saw anything that caught my eye.

The shop has a great concept and vibe, it seems like they've got good customer loyalty with the kind of people that regularly buy the kinds of stuff they've got. If I'm ever in the area it's one of the first shops that I think of (note, there's about a dozen shops in the immediate Mission/SOMA area).